"I hit one, earlier in the year, that went a little bit farther," Stewart said. "But that was probably the best one I hit this year, based on the situation."
Stewart, 23, struggled in his first stint with the Rockies earlier this season, but he has been red hot since being recalled from Triple-A Colorado Springs on July 19. He leads all National League rookies in average, on-base percentage, hits, doubles and RBIs since the All-Star break and has hit safely in 14 of his past 18 games at a .386 clip.
"There's been a little bit of a transformation since he's revisited us," manager Clint Hurdle said. "He's moved upon the opportunity with his performance, and his teammates have embraced him."
Stewart's game-tying shot wouldn't have been possible if not for an unusual double play turned by Barmes in the top of the seventh. With runners at the corners, Emilio Bonifacio hit a grounder to Barmes at third. Ronnie Belliard took a step off the bag, and the third baseman tagged him before throwing out Bonifacio at first to end the threat.
"It all happened real fast," Barmes said. "It was pretty exciting."
The Rockies carried the momentum into a wacky eighth inning that featured six runs, three hits, four walks and two hit batsmen.
With one out in the inning, Matt Holliday hit a bloop double that landed just inside of the right-field foul line. Garrett Atkins walked, and Chris Iannetta was hit by a pitch to load the bases for Brad Hawpe. Hawpe hit the go-ahead, two-run single off Luis Ayala (1-7), and the Rockies busted the game open with four more runs against Washington's shaky relief corps.
"That was a strange inning, no doubt about that," Hurdle said. "And it all started so innocently."
The Nats grabbed an early 1-0 lead after Jesus Flores hit a sacrifice fly to score Austin Kearns in the second. The only other run that De La Rosa surrendered was in the fifth, when he threw a wild pitch that allowed Ryan Langerhans to score from third.
De La Rosa, who gave up seven runs in 1 2/3 innings in his previous start, tossed a season-high seven innings on Tuesday. He showed much improved command with his fastball and kept Colorado in the game by striking out six and giving up just those two runs.
"I did a much better job this time," De La Rosa said. "I stayed relaxed and was able to throw first-pitch strikes."
Reliever Manuel Corpas (2-3) induced an inning-ending double play with two on in the top of the eighth to earn the win.